I have a 6 year old BikeFriday with a Sach Quarz 3 x 7 dual drive. The internal 3 speed hub slips from the largest/easiest gear to the middle gear. Needless to say, on a long steep uphill grade, this is absolutely annoying.

The problem is not simply due to incorrect cable adjustment. I have worked on the problem as have 2 LBS (one is a good shop for folding bikes with internal hubs). We have all come to the conclusion that the Grip shifter needs to be replaced. My problem is that SRAM shifters do not seem compatible with the Quarz hub. One of the LBS spoke with the regional SRAM rep and he also says that the current models do not work with the Quarz hub. If this is the case, that's a shame because the internal hub, when well maintained, should outlast me. Irrespective of how well the hub lasts, it does not matter if there are no shifters.

So here are my questions:

1. Has anyone had the same issue?

2. Are SRAM shifters really not comptaible with Sachs hubs (another real shame since Sachs was around until 5 years ago - not good product support)?

3. Are any other shifters compatible with the Quarz hub?

Your help is appreciated. Without the shifter, I am looking at replacing the entire rear wheel and the shifter.